The present invention relates to a centrifugal high-speed compressor, which drives lubrication free, comprising an internal drive mechanism of a compressor with an impeller on an impeller shaft and with an input shaft, which is driven by a motor or other means of power.
It is well known that a centrifugal compressor is able to compress air to a certain pressure ratio. It is also known that a centrifugal compressor is the most efficient air pump known. The most important part in the centrifugal compressor is the pump wheel or impeller. To work efficiently, however it needs very high rotational speed.
Therefore, a step-up ratio of minimum 6:1 from an input shaft to the impeller is generally. The internal drive mechanism of such a step-up gear typically consists of planetary gears or planetary gear drives. Because gears need lubrication, an oil supply is needed for the step-up transmission. To separate the compressed media from the oil a high-speed seal is needed between the media and the gear.
One way to avoid the oil system is to use a transmission that does not need lubrication. One such example is disclosed in U.S. Pat. No. 6,763,812 B2. However, this design limits the maximum ratio to below 4:1, which is not enough for smaller, efficient high-speed impellers.
The belt drive known from U.S. Pat. No. 6,763,812 B2 has only one cog belt and two sprockets. To cope with the high torque from the input shaft the belt has to be very wide to withstand the high tension in the belt cord. One of the issues in a single belt high-speed belt drive is to evacuate air trapped between the belt and the high-speed sprocket. The wider the belt for increased strength the more difficult is the evacuation of air. If the belt is made narrower and the air can escape to the sides, the belt will not withstand the tension.